Multi-channel fluid dispenser

ABSTRACT

The invention relates to a multi-duct fluid dispenser for withdrawing liquid ( 14 ) from a plurality of cavities ( 12 ) formed in a reservoir platter ( 10 ) and spraying it onto a receiving platter ( 16 ). It comprises:  
     a plurality of flexible ducts ( 26 ) arranged in a convergent bundle, the first ends of which are intended to be immersed in said cavities and the second ends of which are assembled in a miniaturized array,  
     means of filling said ducts, from their first ends, with the liquid contained in the cavities, and  
     means of expelling a drop of liquid from the second end of each duct toward the receiving platter.  
     The ducts are formed in a plurality of flexible plates ( 18 ) joined together by their part ( 24 ) that comprises the second ends of the ducts. They are each formed of two polymer sheets ( 34, 36 ) sealed together and of which at least one is endowed with an array of convergent grooves forming the ducts.

[0001] The present invention relates to the production of miniaturizedhigh-density arrays of samples of biological substances(oligonucleotides, DNA, etc), often known as “biochips”, so that theycan be treated.

[0002] Such arrays are tools that are particularly useful in the fieldof molecular biology, as borne out, in particular, by the publications“High-density oligonucleotides arrays” (A. P. Blanchard etAl.—Biosensors & Biolectronics, Vol. 11, N^(o) 6/7, pp. 686-690, 1996)and “Array of hope” (E. S. Lander—Nature Genetics Supplement, Vol. 21,January 1999).

[0003] The invention relates more specifically to a multi-duct fluiddispenser making it possible to withdraw liquid from a plurality ofcavities formed in a reservoir platter then to deposit an array ofmicrodrops thereof on to a receiving platter as to constitute a“biochip”.

[0004] The dispenser according to the invention is of the typecomprising:

[0005] a plurality of flexible ducts arranged in a convergent bundle,the first ends of which are intended to be immersed in the cavities ofthe reservoir platter and the second ends of which are assembled in aminiaturized array,

[0006] means of filling the ducts, from their first ends, with theliquid contained in the cavities, and

[0007] means of expelling a drop of liquid from the second end of eachduct toward the receiving platter.

[0008] A device of this type is described in document WO 98/29736. Theducts are formed of a bundle of capillary filaments gathered togetheronto an impression head. They are all controlled together.

[0009] Documents U.S. Pat. No. 4,058,146 and EP 0 955 084 proposesimilar embodiments, but the expulsion of liquid is therefore done bysimple contact with the receiving platter. The same is true of thedevice described in document U.S. Pat. No. 4,621,665 but, in this case,there is no change in format between the reservoir platter and thereceiving platter.

[0010] The present invention aims to provide a dispenser thatconstitutes an improved version of the aforementioned systems of theprior art.

[0011] In order to achieve this objective, this dispenser according tothe invention is characterized in that:

[0012] the ducts are formed in a plurality of flexible plates so as toconverge from their first ends toward their second ends;

[0013] these plates are joined together by their part that comprises thesecond ends of the ducts;

[0014] each plate comprises two polymer sheets sealed together and ofwhich at least one is endowed with an array of convergent groovesforming the ducts,

[0015] each duct has a first narrowing near its second end and a secondnarrowing at said end; and

[0016] said expelling means comprise a piezoelectric actuator arrangedon an exterior wall of the duct, between its two narrowings, and thepurpose of which is to deform said at this point so as to reduce thethickness of the duct.

[0017] Advantageously, the dispenser according to the invention also hasthe following main characteristics.

[0018] The reservoir platter is sealed closed by a lid through which theducts pass and the filling means are arranged in such a way as to raisethe pressure in the space lying between the lid and the cavities.

[0019] The filling means comprise a bellows connecting the lid and itsplatter at their periphery.

[0020] The expelling means comprise a second piezoelectric actuatoridentical to the first one and arranged facing it on the other exteriorwall of the duct.

[0021] The piezoelectric actuator is formed as a stack which comprises,starting from the exterior wall of the duct, a lower metal electrode, aninsulating layer, a layer of piezoelectric material, a furtherinsulating layer and an upper metal electrode.

[0022] The expelling means are designed in such a way as to be able toact on each duct individually.

[0023] Other characteristics of the invention will become apparent fromthe description which follows, given with reference to the attacheddrawing in which:

[0024]FIGS. 1 and 2 depict, viewed from the front and from the siderespectively, a dispenser according to the invention,

[0025]FIG. 3 shows, arranged side by side and to scale, a reservoirplatter and a receiving platter;

[0026]FIG. 4 is a view in section of a duct, and

[0027]FIG. 5 shows, in section, the structure of the actuator associatedwith each duct.

[0028]FIGS. 1 and 2 show at 10 a reservoir platter, made of glass orrigid plastic, provided with a plurality of cavities 12 arranged in atwo-dimensional array, in each of which cavities there is a biologicalliquid 14 samples of which need to be deposited, in the form ofmicrodrops, onto a miniaturized receiving platter 16, also made of glassor rigid plastic (nylon).

[0029] It will immediately be seen on referring to FIG. 3 because, forobvious reasons, this is not visible in FIGS. 1 and 2, that the twoplatters are of very different sizes. Typically, the reservoir platter10 has a surface area of about 100 cm² (12.5 cm×8.5 cm) and has 384cavities 12, of a volume of around 100 μl, arranged in a two-dimensionalarray of 16 columns of 24 rows and about 4.5 mm apart, between centers.By contrast, the receiving platter 16 does not have cavities and has asurface area of about 1 cm² only (1.2 cm×0.8 cm).

[0030] In order to withdraw liquid contained in the cavities 12 andspray an array of microdrops thereof onto the receiving platter 16, thedevice according to the invention has a plurality of flexible transferplates 18 joined together. These plates are made of polyimide, forexample, and have a thickness of the order of 50 to 150 μm.

[0031] Each plate 18 has a lower part in the form of an isoscelestrapezium 20, forming a fluid interface, the long base of which isroughly the same length as the width 11 of the reservoir platter 10 andis crenellated in such a way as to end in as many end portions 22 as thereservoir platter has columns of cavities 12, namely 16 in the exampledescribed. The crenellations are sized in such a way that the portions22 can enter the cavities 12.

[0032] The trapezium-shaped fluid interface 20 is extended, from itsshort base, via a rectangular part 24 the length of which correspondsroughly to the width 12 of the receiving platter 16.

[0033] Each flexible plate 18 is provided with a bundle of ducts 26which originate in each of its end portions 22 and terminate, parallelto one another, in the upper part 24. Typically, in the exemplaryembodiment described, the ducts 26 are then 0.5 mm apart, betweencenters.

[0034] The device according to the invention has as many identicalplates 18 as the reservoir platter 10 has rows, namely 24 in the exampledescribed, the end portions 22 of each plate being intended to fit inone of the columns of the platter.

[0035] The flexible plates 18 are gathered together, at their upperpart, parallel to one another, into a frame 28 to form an impressionhead the length of which roughly corresponds to the length L₂ of thereceiving platter 16 and the width of which, as already mentioned,roughly corresponds to its width I₂.

[0036] It goes without saying that the plates could also have a base ofa length that corresponds to the length L₁ of the reservoir platter 10.

[0037] As FIGS. 1 and 2 show, the reservoir platter 10 is sealed closedby a lid 30 through which the flexible plates 18 pass, also withsealing. The sealing around the periphery is provided by a bellows 32,the purpose of which will become apparent later on.

[0038] Reference will now be made to FIG. 4 which shows, on a largerscale, the way in which the flexible plates 18 and their ducts 26 aremade. It can be seen that these plates are formed of two thin sheets ofplastic 34 and 36 of which one, the upper sheet 34 in the figure, hasbeen pre-scored, by any method well known to those skilled in the art,to define the outline of the ducts 26 and which are then joined togetherwith a laminating process, also well known to those skilled in the art.

[0039] Typically, the sheets 34 and 36 have a thickness of 25 to 50 μmand the total volume of the ducts is about 0.5 to 3 μl.

[0040] In their rectangular part 24, the plates 18 comprise, fixed totheir upper sheet 34, facing each duct 26, a piezoelectric actuator 38whose purpose is to deform the sheet at this point so as to reduce thethickness of the duct.

[0041] Above the actuator 38, the duct 26 opens to the outside of thesheet via a narrowing that forms the spout 40, whereas, on the otherside, the duct has a narrowing 42. In the example described, the spout40 and the narrowing 42 have the same depth, from 10 to 40 μm, and thesame width, from 40 to 90 μm. The dimensions of the narrowing may evenbe smaller than those of the spout.

[0042]FIG. 5 shows that the actuator 38 is formed of a stack whichcomprises, starting from the sheet 34, a lower metal electrode 44, aninsulating layer 46, a layer of piezoelectric material 48, a furtherinsulating layer 50 and an upper metal electrode 52. The two electrodesare associated with electrical conductors 54 for controlling theactuator.

[0043] The electrodes 44 and 52 are deposited by evaporation, while theinsulating layers 46 and 50 are deposited by plasma and thepiezoelectric layer 48 is deposited by magnetron-enhanced vapordeposition.

[0044] As depicted in FIG. 1, the electrical conductors powering thevarious actuators 38 end at a control circuit 56 which, under thecommand of a computer 58, energizes them.

[0045] In operation, the assembly formed by the assembled transferplates 18 is placed above the reservoir platter 10 whose cavities 12contain the liquids 14 that are to be transferred onto the receivingplatter 16. Alignment is performed in such a way that having passedthrough the lid 30, each of the end portions 22 of the transfer plates18 lies vertically above a cavity 12. When the ends of the plates areimmersed in the liquid, this liquid is drawn up into the various ducts26 through a capillary effect.

[0046] It is then necessary to press on the lid 30 in order to compressthe bellows 32 so as to raise the pressure in the chamber by a fewmillibar, the pressure being read off a pressure gauge 60. Because ofthis rise in pressure, the liquid continues to rise up inside the ducts26, passes through the narrowings 42, and comes to a halt at the spouts40, through a surface tension effect.

[0047] In order to eject the liquid toward the receiving platter 16, allthat is then required is for the computer 58 to be commanded to apply tothe terminals of the electrodes 44 and 52 of each actuator 38 anelectrical impulse that causes narrowing of the corresponding duct 26.Some of the liquid contained therein, prevented from flowing back by thenarrowing 42, is thus ejected through the spout 40 and sprayed on to thereceiving platter 16, at a clearly defined point.

[0048] The receiving platter 16 can thus receive an array of microdropsof liquid formed at the same number of rows and columns as the reservoirplatter but, as already mentioned, at a greatly reduced scale.Typically, in the example described, the microdrops may have a volumefrom 20 pl to 1 nl.

[0049] Since the plates 18 contain a volume of liquid far greater thanthat of the ejected microdrops, several receiving platters 16 can thenbe used one after another.

[0050] In an alternative form of embodiment that has not been depicted,the ducts 26 could be subjected to the effect of two identical actuators38 arranged face to face on the outside of each of the sheets that formthe flexible plates. Such an arrangement allows better control over thedirection in which the drops are ejected.

[0051] This description has been given with reference to a flexibleplate formed of two sheets sealed together. As an alternative, theplates could be formed of three sheets, the central sheet of which wouldbe pierced with through-openings forming the ducts.

[0052] There is thus produced a liquid dispenser that has the followingmain advantages:

[0053] because the impression head 24 and the fluid interface 20 arecombined as a single piece, the plates 18, the path of the liquid isperfectly uniform and only a minimum amount of dead volume remains;

[0054] because the plates 18 are flexible, it is easier to adapt thedevice to suit reservoir platters 10 and receiving platters 16 ofdifferent sizes;

[0055] because the flexible plates 18 are formed of two polymer sheetsassembled by lamination rather than bonding, any contamination withadhesive of the liquids flowing through the ducts is eliminated;

[0056] because each duct 26 can be controlled individually by an impulsethat ejects a single microdrop, the uniformity in terms of volume of themicrodrops can be guaranteed.

1. A multi-duct fluid dispenser for withdrawing liquid (14) from aplurality of cavities (12) formed in a reservoir platter (10) andspraying it onto a receiving platter (16), comprising: a plurality offlexible ducts (26) arranged in a convergent bundle, the first ends ofwhich are intended to be immersed in said cavities and the second endsof which are assembled in a miniaturized array, means of filling saidducts, from their first ends, with the liquid contained in the cavities,and means of expelling a drop of liquid from the second end of each ducttoward the receiving platter, characterized in that: said ducts (26) areformed in a plurality of flexible plates (18) so as to converge fromtheir first ends toward their second ends; said plates (18) are joinedtogether by their part (24) that comprises the second ends of the ducts,each plate comprises two polymer sheets (34, 36) sealed together and ofwhich at least one is endowed with an array of convergent groovesforming said ducts; each duct (26) has a first narrowing (42) near itssecond end and a second narrowing (40) at said end; and said expellingmeans comprise a piezoelectric actuator (38) arranged on an exteriorwall of the duct, between its two narrowings, and the purpose of whichis to deform said wall at this point so as to reduce the thickness ofthe duct.
 2. The dispenser of claim 1, characterized in that thereservoir platter (10) is sealed closed by a lid (30) through which theducts pass and in that said filling means are arranged in such a way asto raise the pressure in the space lying between the lid and thecavities.
 3. The dispenser of claim 2, characterized in that saidfilling means comprise a bellows (32) connecting the lid (30) and itsplatter (10) at their periphery.
 4. The dispenser of claim 1,characterized in that said expelling means comprise a secondpiezoelectric actuator (38) identical to the first one and arrangedfacing it on the other exterior wall of the duct.
 5. The dispenser ofclaim 1, characterized in that said actuator is formed as a stack whichcomprises, starting from the exterior wall of the duct, a lower metalelectrode (44), an insulating layer (46), a block of piezoelectricmaterial (48), a further insulating layer (50) and an upper metalelectrode (52).
 6. The dispenser of claim 1, characterized in that saidexpelling means (38) are designed in such a way as to be able to act oneach duct individually.
 7. The dispenser of claim 2, characterized inthat said actuator is formed as a stack which comprises, starting fromthe exterior wall of the duct, a lower metal electrode (44), aninsulating layer (46), a block of piezoelectric material (48), a furtherinsulating layer (50) and an upper metal electrode (52).
 8. Thedispenser of claim 3, characterized in that said actuator is formed as astack which comprises, starting from the exterior wall of the duct, alower metal electrode (44), an insulating layer (46), a block ofpiezoelectric material (48), a further insulating layer (50) and anupper metal electrode (52).
 9. The dispenser of claim 4, characterizedin that said actuator is formed as a stack which comprises, startingfrom the exterior wall of the duct, a lower metal electrode (44), aninsulating layer (46), a block of piezoelectric material (48), a furtherinsulating layer (50) and an upper metal electrode (52).
 10. Thedispenser of claim 4, characterized in that said expelling means (38)are designed in such a way as to be able to act on each ductindividually.
 11. The dispenser of claim 5, characterized in that saidexpelling means (38) are designed in such a way as to be able to act oneach duct individually.
 12. The dispenser of claim 7, characterized inthat said expelling means (38) are designed in such a way as to be ableto act on each duct individually.
 13. The dispenser of claim 8,characterized in that said expelling means (38) are designed in such away as to be able to act on each duct individually.
 14. The dispenser ofclaim 9, characterized in that said expelling means (38) are designed insuch a way as to be able to act on each duct individually.